.MKDN File

File extension mkdn is associated with files that contains data in Markdown markup language. Markdown is a lightweight markup language, to write using an easy-to-read, easy-to-write plain text format, then convert it to structurally valid XHTML (or HTML).

How to open:

It seems that you can open or edit .mkdn files using any text editor.

How to convert:

Unless some kind of parser that can transform .mkdn files to other languages (HTML for example) exist it will be hard to convert .mkdn files to anything else.